/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.extensions.euphoria.core.translate;



import com.bff.gaia.unified.sdk.extensions.euphoria.core.client.operator.base.Operator;

import com.bff.gaia.unified.sdk.transforms.PTransform;

import com.bff.gaia.unified.sdk.values.PCollection;

import com.bff.gaia.unified.sdk.values.PCollectionList;

import com.bff.gaia.unified.vendor.guava.com.google.common.base.Preconditions;



import java.util.Optional;



/**

 * Expand operator to a unified {@link PTransform}.

 *

 * @param <InputT> type of input elements

 * @param <OutputT> type of output elements

 * @param <OperatorT> type of operator to expand

 */

public class OperatorTransform<InputT, OutputT, OperatorT extends Operator<OutputT>>

    extends PTransform<PCollectionList<InputT>, PCollection<OutputT>> {



  public static <InputT, OutputT, OperatorT extends Operator<OutputT>> PCollection<OutputT> apply(

      OperatorT operator, PCollectionList<InputT> inputs) {



    final Optional<OperatorTranslator<InputT, OutputT, OperatorT>> maybeTranslator =

        TranslatorProvider.of(inputs.getPipeline()).findTranslator(operator);



    if (maybeTranslator.isPresent()) {

      final PCollection<OutputT> output =

          inputs.apply(

              operator.getName().orElseGet(() -> operator.getClass().getName()),

              new OperatorTransform<>(operator, maybeTranslator.orElse(null)));

      Preconditions.checkState(

          output.getTypeDescriptor() != null,

          "Translator should always return a typed PCollection.");

      return output;

    }



    throw new IllegalStateException(

        "Unable to find translator for basic operator ["

            + operator.getClass()

            + "] with name ["

            + operator.getName().orElse(null)

            + "]");

  }



  private final OperatorT operator;

  private final OperatorTranslator<InputT, OutputT, OperatorT> translator;



  private OperatorTransform(

      OperatorT operator, OperatorTranslator<InputT, OutputT, OperatorT> translator) {

    this.operator = operator;

    this.translator = translator;

  }



  @Override

  public PCollection<OutputT> expand(PCollectionList<InputT> inputs) {

    return translator.translate(operator, inputs);

  }



  public OperatorT getOperator() {

    return operator;

  }

}